Galvanized steel has a long history as an effective and economical material of construction for commercial and industrial water systems, including open loop, closed loop, recirculating, and once-through systems, such as cooling towers, chilled water systems, other evaporative cooling systems. Galvanized steel consists of a thin coating of zinc fused to a steel substrate. White rust is a rapid, localized corrosion attack on zinc that usually appears as a voluminous white deposit. This raid corrosion can completely remove zinc in a localized area with the resultant reduction in equipment life.
There are several known compositions for treating white rust, particularly white rust on galvanized steel components in commercial and industrial water systems. For example, U.S. Pat. Nos. 5,407,597 and 6,468,470 disclose compositions comprising organophosphorus compounds (including 2-phosphonobutane-1,2,4-tricarboxylic acid, “PBTC”), an alkali metal salt of molybdenum, titanium, tungsten, or vanadium, and either a carbamate compound or a tannin compound. U.S. Pat. No. 6,183,649 discloses a white-rust treatment composition comprising PBTC, sodium polyacrylate, sodium tolytriazole, an alkali metal molybdate, and an alkali metal bromide for treating circulating water systems. The '649 patent also discloses the addition of a 1.5% aqueous solution of decyl thioethyletheramine (DTEA) at a rate of 25 lb/1,000 gallons of water/week to the circulating water system prior to adding the white rust treatment composition at a rate of 600 ppm per cycle for ten cycles of recirculation after addition of the DTEA.
Another example is found in U.S. Pat. No. 7,851,655, which discloses white rust treatment compositions comprising various amine compounds, such as the reaction products of Jeffamine® (containing oxypropylene) with glycidol(2,3-epoxy-1-propanol). U.S. Pat. No. 8,585,964 discloses a synergistic blend of 0-10% by weight of an amine-based white rust inhibitor (including those disclosed in the '655 patent) and 10-90% by weight of a benzotriazole. The composition of the '964 may also include a fluorescent tracer to track dosage level.
Other methods used in the field include carbonate ion control by bleed-off or acid use. A problem associated with acid use is that manufacturers typically will not warranty systems if acid is used. Additionally, bleed off control results in more water usage.
Another amine-based corrosion and white rust treatment is disclosed in U.S. Pat. No. 2,333,206. The '206 patent is directed to treatment of metal surfaces in atmospheric conditions (rather than surfaces exposed to flowing water contact in an industrial water system) by applying acrylic, aliphatic amines to metal surfaces to provide a spread thickness of 10,000 to 80,000 sq. ft./lb of amines. One of the amines disclosed in the '206 patent is 9,10-octadecenylamine.